Pilot Project Summary/Abstract The pathogenic potential of TFH is well-described in animal models of lupus and an increased frequency of circulating TFH is associated with disease activity in human patients. Among the risk genes for SLE are several genes associated with metabolic abnormalities that cause increased metabolic activity in T cells. This pilot project is an exploratory project based on the hypothesis that subsets of TFH in SLE patients will have different metabolic alterations that increase their capacity to provide help to B cells. Such cells may be therapeutically targeted by agents that alter cell metabolism. To address these hypotheses, the pilot project proposes two aims; Aim 1 will determine the metabolic profile of CD4+ TFH subsets from SLE patients, and Aim 2 will determine metabolic plasticity of TFH cells. Peripheral blood TFH are a heterogeneous population of CD4+ T cells and express IL-21 but subsets have also been identified that express IFN?, IL-4 or IL-17. Metabolic characterization of these subsets has not yet been performed. We have a hypothesis that TFH cells of SLE patients have altered metabolism and TFH subsets with increased metabolism have an increased capacity to provide B cell help. We will examine 5 different subsets of peripheral TFH based on their expression of PD-1 and the chemokine receptors CXCR5, CCR6 and CXCR3 and examine their metabolic function before and after cell activation using flow cytometry and colorimetric methods that will define their ability to take up glucose, their glycolytic function, their mitochondrial mass and the presence of mitochondrial depolarization. Differences in transcriptome will be determined using RNA-Seq and the ability of each subset to induce B cell differentiation determined. It is already known that TH1, TH2 and TH17 cells have different metabolic requirements and that the different TFH subsets have different functions with respect to their ability to help B cells differentiate into plasma cells. These studies will specifically characterize the metabolic profile of TFH subsets and should generate hypotheses about potential therapies that can be used to interrupt TFH function in a way that could advance precision medicine. As proof of principle, selected metabolic modulators will then be used to determine whether any metabolic functions can be normalized in a subset specific manner and whether this alters T cell helper activity. The pilot project will assist in characterization of TFH proposed by the collaborative project; these two projects are synergistic and could expand under different funding mechanisms to examine how conventional immunotherapies, including TNF inhibitors alter TFH metabolism and function. There is also the potential to relate TFH subsets to the phenotypic characterization of the ANA response proposed in the Principle Project. The pilot project will also benefit from the infrastructure of the ACE project, particularly the access to well characterized patients, uniform methods for blood collection and storage, prioritized access to statistical consultation and a data management plan.